Superabsorbent surface-treated carboxylated polysaccharides and process for producing same

ABSTRACT

Surface-treated carboxyalkylated polysaccharides comprising a biobased content of at least 82% are described herein. The surface-treated carboxyalkylated polysaccharides comprise a CRC of at least 18 g/g, a FSC of at least 26 g/g, and an AUL at 0.7 psi of at least 14 g/g. Processes for the manufacture of surface-treated carboxyalkylated polysaccharides are also described herein.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of U.S. ProvisionalApplication No. 60/826,845 filed on Sep. 25, 2006 and U.S. ProvisionalApplications 60/912,471; 60/912,611 and 60/912,623 filed on Apr. 18,2007 the entire contents of which are incorporated by reference.

FIELD OF THE INVENTION

The present disclosure relates to superabsorbent surface-treatedcarboxyalkyl polysaccharides. More specifically, but not exclusively,the present disclosure also relates to a process for the manufacture ofsurface-treated carboxyalkyl polysaccharides having absorbentproperties. The present disclosure also relates to formulations andhygiene articles comprising surface-treated carboxyalkylpolysaccharides.

BACKGROUND OF THE INVENTION

Water absorbent materials, such as superabsorbent polymers, can beemployed in various applications such as in disposable hygiene articles(e.g. diapers, incontinence articles, feminine hygiene products airlaidsand absorbent dressings); household articles; sealing materials; inoil-drilling fluids (e.g. lost-circulation material, fracturing fluids);anti-condensation coatings; in agricultural, horticultural and forestryapplications for retaining water in the soil and for the release ofwater to the roots of plants and trees; in the textile industry; inprinting applications; in absorbent paper products; in bandages andsurgical pads (e.g. wound dressings); in ore treatments; in concreteproducts; in pet litter; in water treatment; in food pads (e.g.applications related to the transportation of fresh food and foodpackaging); in detergents; in fire-fighting gels; in cloud control; aschemical absorbents for the cleanup of acidic and/or basic aqueousspills including water soluble chemical spills; as polymeric gels forthe slow and controlled release of cosmetics and pharmaceuticals (alsoknown as drug delivery systems); and in the manufacture of artificialsnow. However, the primary use of superabsorbent polymers, also referredas “SAPs”, resides in disposable personal hygiene articles. Suchproducts include, in decreasing order of volume of superabsorbentmaterials used, diapers, training pants, adult incontinence products andfeminine hygiene products.

Carboxyalkyl polysaccharides have been disclosed as superabsorbentmaterials by Ning et al. U.S. Pat. No. 5,247,072; Qin et al. U.S. Pat.No. 5,470,964; U.S. Pat. No. 5,498,705; U.S. Pat. No. 5,550,189; WO01/87365; and Wallajapet et al., US App. 2006/0147689. However, inaddition to being costly, the absorption characteristics of suchmaterials were often insufficient to be useful in the hygiene industry.As a result, synthetic superabsorbent materials such as polyacrylateshave experienced rapid development.

The “Absorbency Under Load” (AUL), as measured at 0.7 psi, constitutes awidely recognized indicator characterizing to the absorption efficiencyof a superabsorbent material. Carboxyalkyl polysaccharides exhibitinghigh AUL values have been previously disclosed by Mertens et al. (USApp. 2004/0157734). However, Mertens is silent with respect to thebiobased content and the carboxyalkylation pattern of thepolysaccharides disclosed. Moreover, Mertens is silent with respect tothe carboxyalkylation process used to manufacture the materialsdisclosed.

Carboxyalkylated starches, produced by means of aqueous processes, havebeen previously disclosed by Gross et al. U.S. Pat. No. 5,079,354;Couture et al. CA 2,362,006; and Theodorus et al. NL 9100249. However,the carboxyalkylated starches were not disclosed as having high AULvalues.

The present disclosure refers to a number of documents, the content ofwhich is herein incorporated by reference in their entirety.

SUMMARY OF THE INVENTION

The present disclosure broadly relates to surface-treated carboxyalkylpolysaccharide particles exhibiting superabsorbent properties.

In an embodiment, the present disclosure relates to superabsorbentsurface-treated carboxyalkyl polysaccharides comprising a biobasedcontent of at least 82% and which polysaccharides have an AUL (asmeasured at 0.7 psi) of at least 14 g/g. In an embodiment of the presentdisclosure, the surface-treated carboxyalkylated polysaccharidescomprise a natural polymeric backbone of an agricultural origin.

In an embodiment of the present disclosure, the surface-treatedcarboxyalkylated polysaccharides comprise a particle ranging in sizefrom 150 μm to 850 μm.

In an embodiment, the present disclosure relates to superabsorbent,internally cross-linked carboxyalkyl polysaccharide particles. In anembodiment of the present disclosure, the internally cross-linkedcarboxyalkyl polysaccharide particles are surface treated.

In an embodiment of the present disclosure, the carboxyalkylatedpolysaccharide is selected from the group consisting of carboxyalkylatedstarches, carboxyalkylated celluloses and carboxyalkylatedgalactomannans. Non-limiting examples of starches include potato, corn,wheat, waxy corn tapioca and mixtures thereof.

In yet a further embodiment, the present disclosure relates tosurface-treated carboxymethyl starch. In an embodiment of the presentthe disclosure, the carboxymethyl starch comprises a homogeneouscarboxymethyl substitution pattern and exhibits an AUL (as measured at0.7 psi) of at least 14 g/g following surface treatment.

In yet a further embodiment, the present disclosure relates to acarboxyalkylated starch obtained by carboxyalkylation in an aqueousalkaline medium. In an embodiment, the carboxyalkylated starch issurface treated.

Moreover, in an embodiment, the present disclosure relates to a processfor the manufacture of surface-treated carboxyalkylated polysaccharidescomprising:

obtaining a carboxyalkylated polysaccharide;

surface-treating the carboxyalkylated polysaccharide using anon-cross-linking acid; and

heating the surface-treated carboxyalkylated polysaccharide.

In an embodiment of the present disclosure, the heating source isselected from the group consisting of an infra-red source and a hot gassource.

In an embodiment of the present disclosure, the process may optionallycomprise an internal cross-linking step, a particle size reducing stepand/or a sieving step.

Moreover, in an embodiment, the present disclosure relates to a processfor the manufacture of surface-treated carboxyalkylated starchcomprising:

dispersing starch in an alkaline medium;

reacting the starch with a carboxyalkylating reagent;

surface-treating the carboxyalkylated starch using a non-cross-linkingacid; and

heating the surface-treated carboxyalkylated polysaccharide.

In an embodiment of the present disclosure, the heating source isselected from the group consisting of an infra-red source and a hot gassource.

In an embodiment of the present disclosure, the carboxyalkylating stepfurther comprises, in a non-specific sequence: (i) adjusting the pH ofthe carboxyalkylated starch; (ii) purifying the carboxyalkylated starch;and (iii) adjusting the moisture content of the carboxyalkylated starch.Moreover, in an embodiment of the present disclosure, the process mayoptionally comprise an alkaline pre-slurrying step, an internalcross-linking step, a particle size reducing step and/or a sieving step.In an embodiment of the present disclosure, the pH of thecarboxyalkylated starch ranges from 6.0 and 10.0.

Moreover, in an embodiment, the present disclosure relates tocarboxyalkylated polysaccharide particles comprising an acidifiedsurface. In a further embodiment of the present disclosure, theseparticles are characterized by the absence of an ester band or an estershoulder as illustrated by ATR-IR spectroscopy.

Moreover, in an embodiment, the present disclosure relates to acarboxyalkylated polysaccharide comprising:

an acidic surface and;

internal cross-linking linkages selected from the group consisting ofionic and ether linkages;

wherein said carboxyalkylated polysaccharide is characterized by thepresence of an ester band as illustrated by ATR-IR spectroscopy.

In yet a further embodiment, the present disclosure relates to a hygienearticle and/or an absorbent member comprising surface-treatedcarboxyalkylated polysaccharide particles.

In yet a further embodiment, the present disclosure relates to anabsorbent member comprising from about 15% to about 80% (W/W) ofsurface-treated carboxyalkyl polysaccharide particles. In a furtherembodiment of the present disclosure, the surface-treated carboxyalkylpolysaccharide particles comprise a biobased content of at least 82%(W/W) as determined by ASTM method D6866-06A. In yet a furtherembodiment, the present disclosure relates to a hygiene articlecomprising an absorbent as described hereinabove. In an embodiment ofthe present disclosure, the hygiene article comprises a thirdacquisition rate of at least 0.22 ml/second and/or an averageacquisition rate of at least 0.12 ml/second. In an embodiment of thepresent disclosure, the hygiene article comprises a third rewet value ofat most 4.0 grams and/or a total rewet value of at most 6.0 grams.

In yet a further embodiment, the present disclosure relates to the useof surface-treated carboxyalkyl polysaccharide particles as absorbentsin disposable sanitary products (e.g. diapers, incontinence articles,feminine hygiene products, airlaids and absorbent dressings); householdarticles; sealing materials; in oil-drilling fluids (e.g.lost-circulation material, fracturing fluids); anti-condensationcoatings; in agricultural, horticultural and forestry applications forretaining water in the soil and for the release of water to the roots ofplants and trees; in the textile industry; in printing applications; inabsorbent paper products; in bandages and surgical pads (e.g. wounddressings), in ore treatments; in concrete products; in pet litter; inwater treatment; in food pads (e.g. applications related to thetransportation of fresh food and food packaging); in detergents; infire-fighting gels; in cloud control; as chemical absorbents for thecleanup of acidic and/or basic aqueous spills including water solublechemical spills; as polymeric gels for the slow and controlled releaseof cosmetics and pharmaceuticals (also known as drug delivery systems),as airlaids; and in the manufacture of artificial snow.

In yet a further embodiment, the present disclosure relates to the useof surface-treated carboxyalkyl polysaccharide particles as absorbentsfor liquids. In an embodiment of the present disclosure, the liquids areselected from the group consisting of water, aqueous solutions,physiological fluids and saline solutions.

Finally, the present disclosure relates to compositions comprisingsurface-treated carboxyalkyl polysaccharide particles and a co-absorbentmaterial.

The foregoing and other objects, advantages and features of the presentdisclosure will become more apparent upon reading of the following nonrestrictive description of illustrative embodiments thereof, given byway of example only with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the appended drawings:

FIG. 1 is a partially sectional schematic side elevational view of ahygiene article in accordance with an embodiment of the presentdisclosure;

FIG. 2 a is a schematic side elevational view of an apparatus formanufacturing an absorbent member in accordance with an embodiment ofthe present disclosure; FIG. 2 b is a cross-sectional view taken alongline 2 b-2 b of FIG. 2 a;

FIG. 3 is an enlarged schematic cross-sectional elevational view of theabsorbent member forming cell of the apparatus of FIG. 2 a;

FIG. 4 is a schematic perspective view of a rewet cylinder for testingthe absorbent members or hygiene articles of the present disclosure;

FIG. 5 shows an attenuated total reflectance infra-red spectrum (ATR-IR)of citric acid surface-treated carboxymethyl starch in accordance withan embodiment of the present disclosure;

FIG. 6 shows an attenuated total reflectance infra-red spectrum (ATR-IR)of hydrochloric acid surface-treated carboxyalkylated starches inaccordance with an embodiment of the present disclosure;

FIG. 7 shows an attenuated total reflectance infra-red spectrum (ATR-IR)of stearic acid surface-treated carboxyalkylated starches in accordancewith an embodiment of the present disclosure;

FIG. 8 shows a Scanning Electron Microscope (SEM) micrograph of dynamicsurface-treated “glass-like” carboxymethyl starch particles inaccordance with an embodiment of the present disclosure;

FIG. 9 shows a Scanning Electron Microscope (SEM) micrograph of staticsurface-treated “glass-like” carboxymethyl starch particles inaccordance with an embodiment of the present disclosure;

FIG. 10 shows a Scanning Electron Microscope (SEM) micrograph ofnon-surface treated porous carboxyalkylated polysaccharide particles inaccordance with an embodiment of the present disclosure;

FIG. 11 shows a Scanning Electron Microscope (SEM) micrograph ofsurface-treated porous carboxyalkylated polysaccharide particles inaccordance with an embodiment of the present disclosure;

FIG. 12 shows a graph illustrating the FSC, CRC and AUL performance of asurface-treated carboxymethyl starch heated in a static environment(convection oven, programmed at 140° C.) over a period of 5 hours inaccordance with an embodiment of the present disclosure;

FIG. 13 shows a graph illustrating the FSC, CRC and AUL performance of asurface-treated carboxymethyl cellulose heated in a static environment(convection oven, programmed at 140° C.) over a period of 2 hours inaccordance with an embodiment of the present disclosure;

FIG. 14 shows a graph illustrating the FSC, CRC and AUL performance of asurface-treated carboxymethyl starch heated in a static environment (IRoven, programmed at 140° C.) over a period of 20 minutes in accordancewith an embodiment of the present disclosure;

FIG. 15 shows a graph illustrating the FSC, CRC and AUL performance of asurface-treated carboxymethyl starch heated in a static environment (IRoven, programmed at 160° C.) over a period of 20 minutes in accordancewith an embodiment of the present disclosure; and

FIG. 16 is a side elevational view of an extruder screw in accordancewith an embodiment of the present disclosure.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

In order to provide a clear and consistent understanding of the termsused in the present specification, a number of definitions are providedbelow. Moreover, unless defined otherwise, all technical and scientificterms as used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which the present disclosure pertains.

The use of the word “a” or “an” when used in conjunction with the term“comprising” in the claims and/or the specification may mean “one”, butit is also consistent with the meaning of “one or more”, “at least one”,and “one or more than one”. Similarly, the word “another” may mean atleast a second or more.

As used in this specification and claim(s), the words “comprising” (andany form of comprising, such as “comprise” and “comprises”), “having”(and any form of having, such as “have” and “has”), “including” (and anyform of including, such as “include” and “includes”) or “containing”(and any form of containing, such as “contain” and “contains”), areinclusive or open-ended and do not exclude additional, unrecitedelements or process steps.

As used in this specification and claim(s), the term “about” is definedas being close to as understood by one of ordinary skill in the art, andin one non-limiting embodiment the term is defined to be within 10%,preferably within 5%, more preferably within 1%, and most preferablywithin 0.5%.

The term “percent” or “%”, unless otherwise specified, refers to apercentage by weight (i.e. % (W/W)).

As used in this specification, the term “saline solution” refers to a0.9% (W/W) sodium chloride solution in deionized water.

As used in this specification, the term “discrete particle” refers toindividual particles.

As used in this specification, the term “homogeneous substitution”refers to carboxyalkylated polysaccharides comprising a substantiallyuniform distribution of carboxyalkyl groups over most of theanhydroglucose units following carboxyalkylation. Typically,homogeneously substituted carboxyalkylated polysaccharides arecharacterized by a standard deviation in the substitution degree of atmost 0.3.

As used in this specification, the term “polysaccharide” refers topolymers having a backbone comprising monosaccharide repeating units.Non-limiting examples include starches, modified starches, amylopectin,modified amylopectin, amylose, modified amylose, cellulose, modifiedcellulose, galactomannans and modified galactomannans.

As used in this specification, the term “monosaccharide unit” refers tocyclic C₅-C₆ aldoses or ketoses. Non limiting examples of C₅-C₆ aldosesinclude allose, altrose, glucose, mannose, gulose, idose, galactose,talose, ribose, arabinose, xylose, and lyxose. Non limiting examples ofC₅-C₆ ketoses include ribulose, xylulose, fructose, sorbose andtagatose.

As used in this specification, the term “Free Swell Capacity” (FSC),also called “Total Absorption”, refers to the amount (g) of fluidabsorbed per gram of the composition. Typical fluids are salinesolutions (0.9% Weight/Weight NaCl solution, hereinafter called 0.9%NaCl solution or saline).

As used in this specification, the term “Centrifuge Retention Capacity”(CRC) also called “Retention”, refers to the amount (g) of fluidretained per gram of the composition, following exposure of thecomposition to a centrifugation force of 250G. Typical fluids are salinesolutions (0.9% Weight/Weight NaCl solution, hereinafter called 0.9%NaCl solution or saline).

As used in this specification, the term “Absorption Under Load” (AUL) at0.7 PSI, also called “Absorption Against Pressure” (AAP) or “AbsorptionUnder Pressure” (AUP) refers to the amount (g) of fluid absorbed pergram of the composition under a given applied pressure. Typical fluidsare saline solutions (0.9% Weight/Weight NaCl solution, hereinaftercalled 0.9% NaCl solution or saline).

As used herein, the term “hygiene article” refers to products designedto absorb fluids, more specifically, physiological fluids. Non limitingexamples of hygiene articles include diapers, incontinence garments andsanitary napkins.

As used herein, the term “absorbent core” refers to the component of thehygiene article that is primarily responsible for liquid handlingproperties of the article, including acquiring, transporting,distributing and storing body liquids.

As used herein, the term “absorbent member” refers to the component ofthe absorbent core that typically provides one or more liquid handlingproperties, e.g., liquid acquisition, liquid distribution, liquidtransportation, liquid storage, etc.

The term “gelatinization” is well known in the art and is generally usedto describe the swelling and hydration of starches.

As used herein, the term “rewet” or “wet-back” is a measure of theabsorbent article's fluid retention capabilities under load. Rewetvalues are reported in grams.

As used in this specification, the term “absorbent material” or“absorbent polymer” refers to materials in a dry, solid state, havinggood fluid-swelling properties and capable of gel forming upon contactwith a fluid. Non limiting examples of such fluids are water, aqueoussolutions, saline, or physiological fluids.

As used in this specification, the term “superabsorbent”,“superabsorbent polymer” or “SAP” refers to absorbent materials capableof gel forming upon contacting with a liquid such as water, aqueoussolutions, saline, or physiological fluids. Such materials arecharacterized by a Centrifuge Retention Capacity (CRC) of at least 15g/g.

As used in this specification, the term “moisture content” refers to theamount of water (% w/w) contained in a material.

As used in this specification, the term “aqueous” is meant to includeany type of reaction medium comprising at least 15% by weight (W/W) ofwater. This includes, but is not limited to, systems comprising waterand optionally one or more co-solvents.

As used in this specification, the term “granular material”, “granules”,“particles”, “powders”, “grains” or “dusts” refers to particulate matterin a finely divided state.

As used in this specification, the term “particle size” refers to thelargest dimension of a particle. The particle size can be directlydetermined using sieving methods, optical or scanning electronmicroscopes as well as by other well-known methods. The particle size isoften considered as diameter of the particle.

As used in this specification, the term “discrete gel particles” refersto superabsorbent particles which, once sufficiently swollen in salinesolution, have the appearance of discrete hydrogel particles.

As used in this specification, the term “surface treated” refers to achemically or physically modified surface.

As used in this specification, the term “cross-linking agent”,“cross-linker” or “exogenous cross-linking agent” refers to an agentwhich in combination with a cross-linkable polysaccharide reacts withthe polysaccharide to produce a cross-linked polysaccharide.Non-limiting examples of cross-linking reactions include the reaction ofthe cross-linking agent with a least two polysaccharide hydroxyl groups;the reaction of the cross-linking agent with a least two polysaccharidecarboxyl groups; and the reaction of the cross-linking agent with apolysaccharide hydroxyl group and a polysaccharide carboxyl group.

As used in this specification, the term reaction efficiency (R.E.)generally refers to the amount (%) of product obtained; relative totheoretical amount based on the initial amount of reagents used.

Very few naturally occurring biopolymers possess adequate gel formingproperties. Biopolymers typically produce gels that, when wet, will forman impermeable layer blocking the flow of fluids. Moreover, theirstructural strength is low, rendering them ineffective for applicationsrequiring high AUL characteristics. Modification of the biopolymerstructure frequently results in undesired reductions of the biobasedcontent. Polysaccharides comprise a class of biopolymer that has beenpreviously used in the absorbent industry. Non-limiting examples ofpolysaccharides include galactomannans, starches and celluloses.

Starch is widely known for its gel forming properties in hot water.Starch-based absorbents have been previously disclosed by Huppé et al.,CA 2,308,537 and Thibodeau et al. CA 2,462,053. However, these materialswere not disclosed as having adequate AUL characteristics. It wassurprisingly discovered that surface-treated carboxyalkylated starchespossess good AUL characteristics, making them suitable as superabsorbentmaterials in the personal hygiene industry.

Starches can be obtained from a variety of sources, including but notlimited to corn, wheat, potato, yam, cassava, rice, millet, sorghum,barley, oats, beans, fava beans, peas, lentils, buckwheat, bananas,arracacha, oca, sago, taro, tapioca, sweet potatoes and mixturesthereof. In an embodiment of the present disclosure, the starches areobtained from a waxy species of, but not limited to, corn, wheat,potato, yam, cassava, rice, millet, sorghum, barley, oats, beans, favabeans, peas, lentils, buckwheat, bananas, arracacha, oca, sago, taro,tapioca, sweet potatoes and mixtures thereof. In an embodiment of thepresent disclosure, the starch is obtained from sources selected fromthe group consisting of corn, waxy corn, potato, tapioca and wheat.

In order to improve the AUL characteristics, the polysaccharides arechemically modified by reaction with a carboxyalkylating agent. In anembodiment of the present disclosure, the carboxyalkylating agentcomprises a carboxymethylating agent. The carboxyalkyl groups may beeither in their neutral carboxylic form or in the form of carboxylateions. As a result of their strongly ionic character, carboxyalkylatedpolysaccharides exhibit strong osmotic forces. An osmotic driving forceis beneficial for obtaining high absorption capacities.

In an embodiment, the carboxyalkylated polysaccharides of the presentdisclosure comprise a pH ranging from 4.5 to 10.0. In a furtherembodiment, the carboxyalkylated polysaccharides of the presentdisclosure comprise a pH ranging from 5.0 to 8.0. The pH of thecarboxyalkylated polysaccharides influences any subsequentsurface-treatment reactions.

Non limiting examples of cations associated with the carboxyalkylatedpolysaccharides of the present disclosure, include monovalent cationssuch as sodium, potassium, ammonium ions and organic ammonium ions. Inan embodiment of the present disclosure, the cation comprises silver.Silver has been previously described as exhibiting anti-microbialproperties (Cullen et al. US 2006/0149182 A1). Superabsorbentscomprising silver carboxymethyl starches are useful as odor inhibitingagents as well as for controlling bacterial growth. Moreover, silvercarboxymethyl starches are suitable for use in wound dressings andsurgical drapes.

In an embodiment of the present disclosure, the carboxyalkylatedpolysaccharides are prepared by Williamson ether synthesis. In anembodiment of the present disclosure, the carboxyalkylating agentcomprises haloacids and/or salts thereof. Non-limiting examples of saltsinclude alkali metal salts. In a further embodiment of the presentdisclosure, the haloacids comprise C₂-C₅ haloacids. In yet a furtherembodiment of the present disclosure, the C₂-C₅ haloacids comprisemonochloroacetic acid, sodium monochloroacetate, potassiummonochloroacetate, lithium monochloroacetate and mixtures thereof.

A typical carboxyalkylation reaction is as follows:

Starch-(OH)₃+mX—(CH₂)_(y)—CO₂Z+WHO→Starch-[(O—(CH₂)_(y)—CO₂Z)_(m)][OH]_(3-m) +mWX

wherein:

Y is an integer ranging from 1 to 4; X is selected from the groupconsisting of Cl, Br and I; W is an alkali metal; m is a numerical valueranging from 0.3 to 1.5; and Z is selected from the group consisting ofH, alkali metal, ammonium and organic ammonium.

In an embodiment of the present disclosure, the carboxyalkylatedpolysaccharides comprise biobased-derived carboxyalkyl substituents. Inan embodiment of the present disclosure, the substituents are derivedfrom biobased haloacids and/or salts thereof. In yet a furtherembodiment of the present disclosure, the biobased haloacid comprisesmonochloroacetic acid. Acetic acid and glycolic acid intermediates areobtained from biobased substrates by fermentation or oxidation (U.S.Pat. No. 4,463,019; U.S. Pat. No. 4,456,622; U.S. Pat. No. 4,569,845;U.S. Pat. No. 3,445,245; U.S. Pat. No. 4,076,844; U.S. Pat. No.4,282,257; U.S. Pat. No. 6,753,170; WO 98/00558; U.S. Pat. No.4,935,360; U.S. Pat. No. 4,656,140; and U.S. Pat. No. 4,503,078). Theintermediates can be halogenated as described in U.S. Pat. No.4,281,184; U.S. Pat. No. 4,383,121; U.S. Pat. No. 7,135,597.

In an embodiment of the present disclosure, the carboxyalkylating agentcomprises non-biobased haloacids or mixtures thereof with biobasedhaloacids and/or salts thereof.

In an embodiment, the present disclosure relates to carboxyalkylatedpolysaccharides comprising a biobased substitution degree of at least0.01. In an embodiment, the present disclosure relates tocarboxyalkylated polysaccharides comprising a total degree ofsubstitution ranging from 0.2 to 1.0. In a further embodiment, thepresent disclosure relates to carboxyalkylated polysaccharidescomprising a total degree of substitution ranging from 0.4 to 0.7.

Alkaline Medium and Carboxyalkylation

The carboxyalkylation of starch was performed by first dispersing thestarch in an alkaline medium. In an embodiment of the presentdisclosure, the starch is dispersed directly in dry alkali.Alternatively, the starch can be dispersed in an aqueous alkalineorganic hydrophilic solvent. In an embodiment of the present disclosure,the organic hydrophilic solvent comprises a C₁-C₅ alcohol. Non-limitingexamples of dry alkali comprise lithium hydroxide, sodium hydroxide,potassium hydroxide and mixtures thereof. In an embodiment of thepresent disclosure, the dry alkali are in powder form. In an embodimentof the present disclosure, the C₁-C₅ alcohol is isopropanol.

Surprisingly, when the carboxyalkylation process was performed in analkaline aqueous medium, superior absorbent characteristics wereobtained for the carboxyalkylated product. Without being bound to anytheory, it is believed that the starch chains and the carboxyalkylatingagents are more labile in an aqueous environment. This increasedmobility provides for a more homogeneous carboxyalkylated substitutionpattern. In an embodiment of the present disclosure, the aqueousalkaline medium comprises a pH of at least 11.0. Typical starch moisturecontents range from 15% to 99%. The propensity for side reactionsbetween the hydroxyl functions and the carboxyalkylating agent increasewith increasing moisture content.

Surprisingly, when the carboxyalkylation process was performed usingreactive extrusion, products exhibiting superior absorbentcharacteristics (AUL at 0.7 psi of at least 14 g/g) were obtained.Moreover, reaction efficiencies of at least 60% could be obtained byreactive extrusion. In an embodiment of the present disclosure, thewater content in the carboxyalkylation-extrusion process ranges from 15%to 30%.

Twin screw extruders are typically used to perform the carboxyalkylationprocess. Twin screw extruders provide for the added flexibility and theshear required to perform the carboxyalkylation reaction. In anembodiment of the present disclosure, dry ingredients such as starch andthe carboxyalkylating agent were fed into the extruder. The ingredientswere the conveyed to an alkali (e.g. alkali hydroxide) injection point,typically located upstream the kneading elements. The alkali may beinjected in the form of a solution. Water may be optionally injected toensure a moisture content ranging from 15% to 30%. In order to limitreagent degradation in the extruder, the temperature is kept below 140°C. The resulting alkaline paste is pumped and kneaded in order toincrease the reaction efficiency. The twin screw extruder may beoptionally equipped with a vent providing for the evacuation ofmoisture. The vent may be placed under vacuum if increased moistureevacuation is desired. The carboxyalkylated starch may be optionallypumped into a die to produce extrudate strands.

In an embodiment of the present disclosure, the carboxyalkylatedpolysaccharides are cross-linked. The cross-linking may be performedbefore, during or after the carboxyalkylation process. In an embodimentof the present disclosure, the cross-linking is performed before thecarboxyalkylation step. A slurry is typically obtained when starch ismixed with water. The slurry-like state is maintained upon the additionof small amount of alkali (pH≦10). The alkaline slurry provides for asuitable reaction medium for the reaction of starch with a covalentcross-linking agent. In an embodiment of the present disclosure, thecross-linking agent comprises epichlorohydrin. Performing thecross-linking prior to the gelatinization step provides for increasedcross-linking reaction efficiency. In an embodiment, the presentdisclosure relates to cross-linked carboxyalkylated polysaccharideshaving a cross-linker content (based on carboxyalkylated polysaccharide)of at most 10%. In a further embodiment, the present disclosure relatesto cross-linked carboxyalkylated starch having a cross-linker content(based on carboxyalkylated starch) of at most 10%.

Cross-linking provides for a starch product having increased molecularweight, increased gel strength and increased resistance to deformationunder stress. An increase in gel strength will result in increases inCRC and AUL. In an embodiment of the present disclosure, cross-linkedpolysaccharides having a molecular weight of at least 500,000 Da wereused.

In an embodiment, the present disclosure relates to carboxyalkylatedpolysaccharides characterized by a FSC of at least 25 g/g, a CRC of atleast 18 g/g and an AUL at 0.7 Psi of at least 14 g/g.

Purification

The purity of the carboxyalkylated product is of importance. Asimportant amounts of salt are produced during the carboxyalkylationstep, any residual impurities may lead to “salt poisoning”, which willhave the effect of reducing the absorption performance of thecarboxyalkylated product. The carboxyalkylated product can be purifiedby washing with a water miscible organic solvent and/or water miscibleorganic solvent/water mixtures. Non-limiting examples of water miscibleorganic solvents include C₁-C₄ alcohols. The washed carboxyalkylatedproduct is subsequently filtered and dried. The purification process iscontinued until no further salt precipitation can be observed from thewashings when mixed with AgNO₃. The conductivity of the washingsrepresents a further indication of the purity of the carboxyalkylatedproduct. The conductivity should be at most 1,500 μS/cm.

In an embodiment of the present disclosure, the carboxyalkylated productwas purified under acidic conditions. The first step typically comprisesan acidification procedure. The carboxylate groups were converted intocarboxylic groups. The acidified carboxyalkylated polysaccharides willtypically exhibit a pH ranging from 4.5 to 6.5. The acidifiedcarboxyalkylated product was then heated, as the heated product issubstantially insoluble in water. Instead, the product will swell andform a hydrogel or hydrogel particles. The gel particles weresubsequently washed with water, or acidic solutions, to remove anyresidual salts. The purification process was continued until no furthersalt precipitation could be observed from the washings when mixed withAgNO₃. The conductivity of the washings represents a further indicationof the purity of the carboxyalkylated product. The conductivity shouldbe at most 1,500 μS/cm.

Adjusting pH and Moisture

In order to obtain a suitable carboxylate content, the pH of thepurified carboxyalkylated polysaccharide may be adjusted to be within6.0 to 10.0. In an embodiment of the present disclosure, the pH may beadjusted in water miscible organic solvents.

Reactive extrusion may also be used to adjust the pH of thecarboxyalkylated polysaccharide. In an embodiment of the presentdisclosure, the pH is adjusted following the carboxyalkylation reactionbut before the extruder discharge. The pH can be adjusted by injectingan acidic solution into the carboxyalkylated polysaccharide paste. In anembodiment of the present disclosure, the paste comprises acarboxyalkylated starch. The acidified paste mixture was subsequentlyconveyed and pumped into a section of the extruder comprising a furtherseries of kneading elements, accomplishing the pH adjustment of thepolysaccharide product. Following the pH adjustment, the product wasconveyed, pumped and discharged from the extruder. The twin screwextruder may be optionally equipped with a vent providing for theevacuation of moisture. The vent may be placed under vacuum if increasedmoisture evacuation is desired. The product may be optionally pumpedinto a die to produce extrudate strands.

The moisture content of the carboxyalkylated product may be furtheradjusted. In an embodiment of the present disclosure, the moisturecontent of the carboxyalkylated product is of at most 7%. Non-limitingexamples of moisture lowering techniques comprise conduction heating,vacuum evaporation, convection heating and infra-red heating. It isbelieved to be within the capacity of a skilled technician to selectother suitable moisture lowering techniques.

Particle Formation

In an embodiment of the present disclosure, the carboxyalkylatedpolysaccharides comprise a particulate matter. In a further embodimentof the present disclosure, the carboxyalkylated starches comprise aparticulate matter. In yet a further embodiment of the presentdisclosure, the carboxyalkylated starches are “glass-like”. In yet afurther embodiment of the present disclosure, the carboxyalkylatedstarches comprise a “porous” structure. The particulate structure of thecarboxyalkylated product is influenced by the pH adjustment, thepurification procedure and the moisture adjustment. The particulatestructure of the carboxyalkylated product will also influence the bulkdensity, frangibility and abrasiveness. In an embodiment, thecarboxyalkylated starch product of the present disclosure comprises abulk density ranging from 0.5 g/cm³ to 0.7 g/cm³.

In an embodiment of the present disclosure, the size of thecarboxyalkylated polysaccharide particles is reduced. Sieving comprisesa convenient technique to control the particle size. The absorptionperformance of the carboxyalkylated polysaccharide particles is linkedto their particle size. Particles having a size of at least about 150 μm(100 Mesh) will limit gel blocking. Particles having a size of at mostabout 850 μm (20 Mesh) will limit pinhole formation in hygiene productsand will swell more efficiently.

Surface Coating

Under high pressures, such as 0.7 psi, gel particles will have atendency to collapse and form “disc-shaped” gel particles. These“disc-shaped” particles will severely impede the absorption process andmay eventually lead to gel blocking. More rigid gel particles willprovide increased resistance to deformation and will maintain anadequate swelling rate. Surface treated carboxyalkylated polysaccharideparticles exhibit absorbent properties (FSC, CRC) similar to lightlycross-linked carboxyalkylated polysaccharides, while having enoughstructural rigidity to swell under pressure (AUL).

Surface treatment agents will decrease the water solubility of thesurface of the carboxyalkylated polysaccharide particles. Moreover,surface treatment agents will give to the carboxyalkylatedpolysaccharides, once swollen, the appearance of discrete gel particles.Surface treatment will also increase the AUL at 0.7 Psi. Surfacetreatments are typically effected upon heating. Non-limiting examples ofsurface treatment agents include cross-linkers, non-cross-linking acidsand combinations thereof. Non-limiting examples of non-cross-linkingacids include monovalent acids. These acids may be derived from mineralsources, from non-biobased sources or from biobased sources. In anembodiment of the present disclosure, the non-cross-linking acids areselected from the group consisting of hydrochloric acid, acetic acid,glycolic acid and stearic acid.

Higher AUL values (at 0.7 Psi) are typically obtained with increasedsurface-treatment. However, care should be taken to not adversely affectother important SAP characteristics such as the FSC and CRC. In anembodiment of the present disclosure, the amount of non-crosslinkingacid reagent ranges from about 0.01 milliequivalent to about 20.0milliequivalents per gram of carboxyalkylated polysaccharide (meq/g). Ina further embodiment of the present disclosure, the pH of thesurface-treated carboxyalkylated polysaccharide ranges from about 4.5 to6.5.

In an embodiment of the present disclosure, the surface of thecarboxyalkylated polysaccharides is treated with a cross-linking agent.Non-limiting examples of cross-linking agents include citric acid,aluminum ions (Al³⁺) and epichlorohydrin. Treatment with citric acidwill result is the formation of ester linkages; treatment withepichlorohydrin will result in the formation of ether linkages; andtreatment with aluminum ions. In a further embodiment of the presentdisclosure, the pH of a citric acid surface-treated carboxyalkylatedpolysaccharide ranges from about 4.5 to 6.5.

In an embodiment of the present disclosure, the surface treatment isperformed by treating the surface of the carboxyalkylatedpolysaccharides with a solution comprising the surface treatment agent.In order to achieve an adequate particle surface treatment, thepenetration depth of the surface treatment agent should be carefullycontrolled. Such control can be achieved by the careful selection of anappropriate solvent system. Non-limiting examples of such solventsystems include hydrophilic organic solvents and hydrophilic organicsolvent/water mixtures. The use of an organic hydrophilic solvent willlimit surface treatment agent diffusion and surface swelling of thecarboxyalkyl polysaccharide particles. Typical hydrophilic organicsolvents comprise C₁-C₅ alcohols. In an embodiment of the presentdisclosure, the hydrophilic organic solvent comprises isopropanol. In anembodiment of the present disclosure, hydrophilic organic solvent/watermixtures are used. In a further embodiment of the present disclosure,the mixture comprises a solvent/water ratio ranging from 50/50 to 95/5.The water in these mixtures provides for increased surface penetration.

In an embodiment of the present disclosure, the carboxyalkylatedpolysaccharide particles are mixed with the solvent having dissolvedtherein the surface treatment agent. A wet powder or a paste istypically obtained. The paste or wet powder may optionally be comminutedprior to heating. Prior to heat treatment, the solvent may optionally beevaporated. The solvent evaporation step is typically performed attemperatures of not more than 100° C.

In an embodiment of the present disclosure, the surface treatment wasperformed by applying droplets of a solution comprising the surfacetreatment agent to the surface of the carboxyalkylated polysaccharideparticles. Non-limiting examples of solvent systems include hydrophilicorganic solvents and hydrophilic organic solvent/water mixtures. It wassurprisingly discovered that aqueous solutions are suitable under suchconditions. In order to avoid particle swelling, the aqueous solutionshould be rapidly evaporated following droplet application. In anembodiment of the present disclosure, evaporation was achieved by meansof gas circulation around the particles. In a further embodiment of thepresent disclosure, the gas has a temperature of at least 40° C.Particle swelling is substantially avoided when the droplet applicationflow is at least equivalent to the solvent evaporation rate. Such anenvironment can be achieved in an agglomerator or on a fluidized beddryer equipped with spraying nozzles.

Heat Treatment

Most surface treatment agents require a heating step. Surface treatmentresults in a product exhibiting good AUL values (at 0.7 psi).

The heat treatment may be accomplished using an electromagneticradiation source, a hot gas or a heated surface. In an embodiment of thepresent disclosure, convection (hot gas) or Infra-Red (electromagneticradiation) heating is used. Typically, IR sources identified as mediuminfra-red or carbon infra-red are well suited. In an embodiment of thepresent disclosure, the surface treated carboxyalkylated polysaccharidesare heated to temperatures of at least 140° C. In a further embodimentof the present disclosure, the surface treated carboxyalkylatedpolysaccharides are heated to temperatures of at least 160° C. In yet afurther embodiment of the present disclosure, the moisture content ofthe surface treated carboxyalkylated polysaccharide particles followingheat treatment is less than 5%. Care should be taken not to overheat theparticles. Overheating is typically characterized by browning of theparticles.

In an embodiment of the present disclosure, the heat treatment wasaccomplished in a static environment. Non-limiting examples of staticenvironments include immobile environments, belt-conveyed environments,sliding environments or any environment that substantially avoidsinducing undue interaction (i.e. shearing) between the particlesthemselves or between the particles and other objects. In an embodimentof the present disclosure, the static environment comprises a surfaceover which the particles are evenly spread. Such a surface is typicallyan IR transmitting surface such as glass or Pyrex™.

The carboxyalkylated polysaccharides of the present disclosure may besurface treated with may types of acids. When non-crosslinking acids areused, ester linkages are typically not observed by ATR-IR spectroscopy.The absence of an ester band (between 1750 cm⁻¹ and 1715 cm⁻¹) was notedin the case of hydrochloric acid surface treated carboxyalkylatedstarches (FIG. 6). The presence of a shoulder was observed for stearicacid surface treated carboxyalkylated starches (FIG. 7).

In an embodiment, the present disclosure relates to internallycross-linked carboxyalkylated polysaccharides. These polysaccharides mayalso be surface-treated by exposure to surface treating agents.

In an embodiment of the present disclosure, the surface-treatedcarboxyalkylated starches have an AUL at 0.7 Psi of at least 14 g/g. Inan embodiment of the present disclosure, the surface-treatedcarboxyalkylated starches have an AUL at 0.7 Psi of at least 14 g/g anda CRC of at least 18 g/g. In an embodiment of the present disclosure,the surface-treated carboxyalkylated starches have an AUL at 0.7 Psi ofat least 14 g/g, a CRC of at least 18 g/g and a FSC of at least 25 g/g.In a further embodiment of the present disclosure, the surface-treatedcarboxyalkylated starches are characterized by a bulk density rangingfrom 0.5 g/cm³ to 0.7 g/cm³.

The surface-treated carboxyalkylated polysaccharides form discrete gelparticles once swollen. The propensity to form discrete gel particlesmakes these materials especially suitable for use in hygiene articles.Indeed, when incorporated into absorbent members, discrete gel particlesupon swelling to their maximum extend, provide for enhanced water flow.This characteristic significantly increases the wet porosity of theabsorbent articles and thus improved liquid absorption and diffusion.

In an embodiment of the present disclosure, the surface-treatedcarboxyalkylated starches have an AUL at 0.7 Psi of at least 14 g/g anda biobased content, according to ASTM D 6866-06 A, of at least 82%. Inan embodiment of the present disclosure, the surface-treatedcarboxyalkylated starches have an AUL at 0.7 Psi of at least 14 g/g anda biobased content, according to ASTM D 6866-06 A, of at least 87%. Inan embodiment of the present disclosure, the surface-treatedcarboxyalkylated starches have an AUL at 0.7 Psi of at least 14 g/g anda biobased content, according to ASTM D 6866-06 A, of at least 95%.These surface-treated carboxyalkylated starches are suitable for use inhygiene articles and absorbent members.

The surface-treated carboxyalkylated polysaccharides of the presentdisclosure may be mixed with other co-absorbent materials to provideabsorbent compositions. In an embodiment, the absorbent compositionscomprise from about 1 to about 99% (w/w) of surface-treatedcarboxyalkylated polysaccharides and from about 99 to about 1% (w/w) ofco-absorbent material. Non-limiting examples of co-absorbent materialsinclude synthetic absorbent polymers, starch-based absorbents, mannosecontaining polysaccharides, fibers and mixtures thereof.

The surface-treated carboxyalkylated starch of the present disclosuremay be mixed with other co-absorbent materials to provide absorbentcompositions. In an embodiment, the absorbent compositions comprise fromabout 1 to about 99% (w/w) of surface-treated carboxyalkyl starches, andfrom about 99 to about 1% (w/w) of co-absorbent material. Non-limitingexamples of co-absorbent materials include synthetic absorbent polymers,starch-based absorbents, mannose containing polysaccharides, fibers andmixtures thereof.

Non-limiting examples of starch-based absorbents include glass-likestarches such as disclosed by Huppé et al. (CA 2,308,537); amylopectinnetworks such as disclosed by Thibodeau et al. (CA 2,462,053);polysaccharide agglomerates such as disclosed by Chevigny et al. (CA2,534,026); hydroxyethyl starch; hydroxypropyl starch; starchnanocomposites such as disclosed by Berrada et al. (CA 2,483,049); andmixtures thereof.

Non-limiting examples of mannose containing polysaccharides include guargum, tara gum, locust bean gum, konjac, mesquite gum, psyllium extracts,fenugreek extracts and mixture thereof. The mannose containingpolysaccharides may be chemically or enzymatically modified (i.e.mannose derivatives), cross-linked or in the form of nanocompositematerials.

Non-limiting examples of fibers include cellulose, viscose, rayon,cellulose acetate, polyamides (i.e. Nylon™), polyalkylenes,polyethylene, polypropylene, bi-component fibers, polyesters,polylactides, polypropanediols, polyhydroxyalkanoates, Lyocell™,sphagnum and mixtures thereof.

The synthetic absorbent polymers to be used as co-absorbent materials inthe absorbent compositions of the present disclosure, are generallyobtained from the polymerization, typically by radical or radical graftpolymerization, of monomers, non-limiting examples of which includeacrylic acid, acrylate salts, acrylic ester, acrylic anhydride,methacrylic acid, methacrylate salts, methacrylic esters, methacrylicanhydride, maleic anhydride, maleic salts, maleate esters, acrylamide,acrylonitrile, vinyl alcohol, vinyl pyrrolidone, vinyl acetate, vinylguanidine, aspartic acid, aspartic salts and mixtures thereof.

The surface-treated carboxyalkylated polysaccharide particles of thepresent disclosure, or compositions comprising such particles, aresuitable for use in methods for absorbing liquids. In an embodiment ofthe present disclosure, one or more of thesurface-treated-carboxyalkylated polysaccharides are contacted with aliquid to be absorbed. Non-limiting examples of liquids include water,aqueous solutions, physiological fluids and saline solutions. Thesurface-treated carboxyalkylated polysaccharides of the presentdisclosure, upon contacting with the liquid(s) to be absorbed, will forma gel trapping the liquid(s) within.

The surface-treated carboxyalkylated starch particles of the presentdisclosure, or absorbent compositions comprising such particles, aresuitable for use in methods for absorbing liquids. In an embodiment ofthe present disclosure, one or more of thesurface-treated-carboxyalkylated starches are contacted with a liquid tobe absorbed. Non-limiting examples of liquids include water, aqueoussolutions, physiological fluids and saline solutions. Thesurface-treated carboxyalkylated starches of the present disclosure,upon contacting with the liquid(s) to be absorbed, will form a geltrapping the liquid(s) within.

These surface-treated carboxyalkylated polysaccharides of the presentdisclosure are suitable for use in hygiene articles, including diapers,incontinence products and sanitary napkins. In an embodiment of thepresent disclosure, the surface-treated carboxyalkylated polysaccharideis a surface-treated carboxyalkylated starch. A typical hygiene articleis illustrated in FIG. 1. The article comprises a backsheet A, atopsheet B and an absorbent core C. The absorbent core is typicallydisposed between the top- and bottom sheets. The top- and bottom sheetsmay provide a sealing envelope for the absorbent core. The backsheet istypically an impermeable film composed of a plastic material. Thetopsheet is typically a porous, water permeable, water insoluble, filmor non-woven material. An acquisition distribution layer(non-illustrated) may optionally be disposed between the topsheet andthe absorbent core. The acquisition-distribution layer provides for thediffusion of liquids into the absorbent core, increasing both the stainarea and the absorption speed.

The absorbent member constitutes the component of the absorbent corethat is responsible for absorbing urine and physiological fluids whenused in the context of hygiene articles. In an embodiment of the presentdisclosure, the absorbent members comprise cellulose fluff pulp fibersand surface-treated carboxyalkylated polysaccharides. The components canbe uniformly mixed in an air-dispersion. The absorbent members mayoptionally further comprise additives such as fragrances, odor controlagents, binders, thermoplastic fibers, cross-linkers and fillers. In anembodiment of the present disclosure, the absorbent members arecompressed in order to reduce their bulkiness. In a further embodimentof the present disclosure, the absorbent members have a density of atleast 0.10 g/cm³. In an embodiment, the absorbent members of the presentdisclosure comprise a surface-treated carboxyalkylated polysaccharidecontent ranging from 15% to 80%. In a further embodiment, the absorbentmembers of the present disclosure comprise a surface-treatedcarboxyalkylated polysaccharide content ranging from 30% to 60%.

The hygiene articles comprising the absorbent members of the presentdisclosure exhibit surprisingly good absorbent characteristics. Thesurface-treated carboxyalkylated polysaccharides, as contained withinthe absorbent members, are characterized by a biobased content,according to ASTM D 6866-06 A, of at least 82%. The averaged and thirdacquisition rates are widely accepted indicators when assessing theabsorbency characteristics of a hygiene article. In an embodiment of thepresent disclosure, the hygiene articles comprise a third acquisitionrate of at least 0.22 ml/sec and an averaged acquisition rate of atleast 0.12 ml/sec. The third rewet and the total rewet compriseindicators for assessing the quality of a hygiene article. In anembodiment of the present disclosure, the hygiene articles comprise athird rewet value of at most 4.0 g. In a further embodiment of thepresent disclosure, the hygiene articles comprise a third rewet value ofat most 1.5 g. In an embodiment of the present disclosure, the hygienearticles comprise a total rewet value of at most 6.0 g. In a furtherembodiment of the present disclosure, the hygiene articles comprise atotal rewet value of at most 2.5 g.

The surface-treated carboxyalkylated polysaccharides of the presentdisclosure may also be used in other applications such as in food pads;in agricultural, horticultural and forestry applications for retainingwater in the soil and for the release of water to the roots of plantsand trees; in the textile industry; in printing applications; inabsorbent paper products; in ore treatments; in concrete additives; inpet litter; in water treatment; in cloud control; in drilling fluids(e.g. lost circulation materials, fracturing fluids); in food pads (e.g.applications related to the transportation of fresh food and foodpackaging); in detergents; anti-condensation coatings; in fire-fightinggels; in sealing materials; in bandages and surgical pads (e.g. wounddressings); as chemical absorbents for the cleanup of acidic and/orbasic aqueous spills including water soluble chemical spills; aspolymeric gels for the slow and controlled release of cosmetics andpharmaceuticals (also known as drug delivery systems), and finally inthe manufacture of artificial snow.

EXPERIMENTAL Materials

Potato starch was obtained from Penford Food Ingredients (Centennial,Colo.). Grade A wheat starch (Whetstar™ 4) was obtained from ArcherDaniels Midland (Decatur, Ill.). Epichlorohydrin, sodiummonochloroacetate, citric acid monohydrate, stearic acid, acetic acid,research grade isopropanol and sodium hydroxide were obtained fromSigma-Aldrich (St-Louis, Mo.). Hydrochloric acid and methanol wasobtained from Labmat (Quebec City, Canada).

Infra-Red Thermometer

A TES 1326S infra-red thermometer was used.

Convection Oven

A Lab tray drier TY 2, National Drying Machinery Company, (Philadelphia,USA) was used.

Infra-Red Oven

A Panasonic NB-G100P infra-red oven was used.

Grinder

A Braun™ model KSM grinder was used to grind the samples.

Extruder (CMC)

A Baker-Perkins MPF-50D (50 mm) twin screw extruder was used tomanufacture CMC hydrogels. The extruder was equipped with a ME-IIAccurate Power Feeder. An injection nozzle was positioned 381 mmdownstream the extruder. No die was used. The extruder had the followingscrew design:

TABLE 1 TSE Screw Design Element type Element length (mm) BeginningSpacer 6.35 Spacer 101.6 Conveying 76.2 Pumping 50.8 Kneading 12.7Pumping 50.8 Conveying 76.2 Pumping 50.8 Pumping 25.4 Exit Port

Extruder (CMS)

In an embodiment of the present disclosure, a Leistritz ZSE 40 HP (40mm) twin screw extruder was used to manufacture carboxyalkylatedpolysaccharides. The extruder L/D ration was set at 40. Thepolysaccharide (e.g. starch) was fed into the TSE using an Acrisongravimetric agitated feeder (405-170-OE). Sodium monochloroacetate wasfed into the TSE using an Acrison gravimetric feeder (405-1015-C).Starch and sodium monochloroacetate were into the TSE at positionslocated between 30 mm and 180 mm downstream the extruder. A sodiumhydroxide injection nozzle, equipped with a Cole-Parmer peristalticpump, was positioned 560 mm downstream the extruder. Closed side stufferbarrels were positioned at a location between 640 mm and 800 mmdownstream the extruder. A vent was positioned at a location between1120 mm and 1280 mm downstream the barrel. No die was used. The extruderhad the following screw design:

TABLE 2 TSE Screw Design Pitch length (mm) Element length (mm) Kneadingblock angle (°) Extruder's beginning 20 mm 30 mm 60 mm 150 mm  30 mm 60mm 45 mm 150 mm  45 mm 150 mm  45 mm 50 mm 45 mm 50 mm 30 mm 60 mmKneading block 60 mm 60° 6 elements (forward) Kneading block 60 mm 60° 6elements (forward) 45 mm 30 mm 45 mm 60 mm Kneading block 60 mm 90° 6elements Kneading disc 10 mm Kneading disc 10 mm 60 mm 150 mm  45 mm 150mm  45 mm 60 mm 45 mm 60 mm Extruder's discharge

All extruder elements were double flighted. The kneading elementthickness was 2 mm.

Agglomerator

A STREA-1 model from Niro Pharma Systems (Fluid bed laboratory unit),equipped with a film coater nozzle, was used. The STREA-1 model wasconfigured with the injection nozzle located laterally; the nozzlefacing upside down.

Apparatus Used to Manufacture the Absorbent Member

FIG. 2 a illustrates an apparatus for the manufacture of an absorbentmember. Fluff pulp fibers and surface-treated carboxyalkylatedpolysaccharide were conveyed into the apparatus and deposited on anon-woven filter using a high velocity air stream. The air stream wasprovided using a compressor (790 KPa) connected to the apparatus througha flexible hose (1). A pressurized air regulator was connected to thecompressor. Fluff pulp fibers and surface-treated carboxyalkylatedpolysaccharides (e.g. surface treated carboxyalkylated starch) areintroduced into a first mixing chamber (2) of the absorbent-core formingapparatus using a funnel (3). The fluff pulp fibers and thesurface-treated carboxyalkylated polysaccharide (e.g. surface treatedcarboxyalkylated starch) were thoroughly mixed in the mixing chamberusing a 6-bladed propeller (4) connected to an electric motor (5). Thepropeller was located above a 4-Mesh screen (6). In an embodiment of thepresent disclosure, the propeller was located 59 mm above the 4-Meshscreen (6). A brush (10) was positioned above the screen; the brushrubbing against the screen. Particles small enough to pass through thescreen were transported to a second mixing chamber (7) using an airflow, from which they were conveyed into an absorbent member-formingcell (8) (illustrated in greater detail in FIG. 3). An air vacuumchamber (9) was positioned underneath the absorbent member-forming cell(8). The vacuum chamber (9) was connected to a vacuum cleaner (notshown). The absorbent member-forming process can be observed through avisualization window (11).

FIG. 3 illustrates an enlarged view of the absorbent member-formingcell. A funnel (36) was positioned over a molding cell (37) in which theabsorbent member (40) was produced. A 20-Mesh screen (38) was positionedat the bottom of the molding cell (37). A Maquin S.A. 20 g/m² non-wovenfilter (39) was positioned between the molding cell (37) and the screen(38) for retaining fine fluff and fine polysaccharide particles. Airpassing through the molding cell (37) was conveyed to a vacuum chamber(9). Upon completion of the process, the molding cell (37) was removedusing a handled plate (41).

Rewet Cylinder

FIG. 4 illustrates a rewet cylinder (50) for testing the rewetcharacteristics of the absorbent members or hygiene articles of thepresent disclosure. The opposing ends (10 cm diameter) (51) of thecylinder were composed of Plexiglas™ and contained a central orifice(52) measuring 2.5 cm in diameter. The opposing ends of the cylinder hada surface area of 78.5 cm². An inner co-axial cylinder (53) is disposedwithin the rewet cylinder (50) defining a cylindrical space (54)therebetween. A weight (55), supported by two screws (56), was disposedwithin the cylindrical space (54). In an embodiment of the presentdisclosure, the rewet cylinder (50) weighed 3.87 kg. In operation, theinner cylinder (53) was filed with water (57).

Test Methods

As discussed in Modern Superabsorbent Polymer Technology (Buchholz, F.L. and Graham, A. T. Eds., Wiley-VCH, New York, 1998, section 4.6.1.Swelling Capacity: Theory and Practice, p. 147), several measurementmethods are used to characterize the swelling capacity of a polymer. Inthe field of superabsorbents, the Gravimetric Swelling Capacity [alsocalled the Free Swell Capacity (FSC)] and the Centrifuge Capacity [alsocalled the Centrifuge Retention Capacity (CRC)] are recommended methods.The FSC and the CRC were used to characterize the swelling capacities ofthe absorbent products of the present disclosure.

Tea Bags for FSC and CRC Measurements

Tea bags (10×10 cm) were made from heat sealable Ahlstrom (ChirnsideDuns, UK) filter paper (16.5±0.5 g/m²) grade 07291.

FSC Measurements

The Free Swell Capacity (FSC) in a 0.9% NaCl solution was determinedaccording to the recommended test method WSP 240.2 (05) A from WorldwideStrategic Partners (EDANA-INDA).

CRC Measurements

The Centrifuge Retention Capacity (CRC) in a 0.9% NaCl solution wasdetermined according to the recommended test method WSP 241.2 (05) Afrom Worldwide Strategic Partners (EDANA-INDA).

AUL Measurements

The Absorption Under Load (AUL) at 0.7 Psi, in a 0.9% NaCl solution wasdetermined according to the recommended test method WSP 242.2 (05) Afrom Worldwide Strategic Partners (EDANA-INDA).

Biobased Content

The biobased content of the surface-treated carboxyalkylatedpolysaccharides of the present disclosure was determined bycharacterization of the modern radiocarbon content. Radiocarbonconcentrations are provided as fractions of the modern standard d¹⁴C,following the conventions of Stuiver and Polach (Radiocarbon, v. 19, p.355, 1977). All results have been corrected to account for isotopicfractionation according to the conventions of Stuiver and Polach (1977),with d¹³C values measured on prepared graphite using an AMSspectrometer. These values can differ from the d¹³C values obtained forthe original material, if fractionation occurred during samplegraphitization or the AMS measurement. Because the biobased content isgiven as “pre-bomb values”, all ratios were multiplied by 93 (100%×0.93)to reflect biobased percentages.

A precise amount (between 5 to 10 mg) of surface-treatedcarboxyalkylated polysaccharide was collected and transferred into aquartz tube comprising metallic silver and cupric oxide. The quartz tubewas placed under vacuum, sealed and combusted at 850° C. over a periodof 1 hour. The furnace was cooled (1° C./minute), until the sample wasat 400° C.

The carbon dioxide product was then purified. In an embodiment of thepresent disclosure, the purification is accomplished by placing thequartz tube in a sealed tube cracker (as illustrated in ASTM D 6866-06A)under vacuum. The tube cracker was then immersed in a Dewar comprisingliquid nitrogen. The tube was cryogenically cracked, allowing anyunfrozen gases to escape. An alcohol/dry ice mixture was then placedaround the tube cracker, sublimating the carbon dioxide content. Thesublimated carbon dioxide was then transferred into a stainless steeltube (volume known) possessing a stopper. This stopper was closed andother gases were allowed to escape from the tube cracker. The stainlesssteel tube was then connected to a vacuumed Pyrex™ tube. The stainlesssteel tube was allowed to reach room temperature and the pressureobserved. The carbon dioxide was allowed to enter the Pyrex™ tube. Thebottom portion of the Pyrex™ tube was immerged in liquid nitrogen andthe top portion sealed. The tubes were sent to an AMS facility fordetermination of the ¹⁴C ratios.

Scanning Electron Micrographs

Scanning electron micrographs were recorded using a Hitachi® S 3000Nscanning electron microscope. Samples were placed on two-sided adhesivepaper, glued to an aluminum plate. Any non-glued particles were removedusing an air jet. A thin (about 10 nm) gold layer was then applied tothe surface of the glued sample using a sputter coater. The surface wasthen scanned and recorded.

Prototype Hygiene Article Manufacture

Hygiene articles were prepared by a process using the absorbent memberforming apparatus (FIGS. 2 and 3). Bleached sulphate fluff pulp (8.5 g,SoLoNo™, Weyerhaeuser, Fereral Way, Wash.) was humidified in a roomhaving a relative humidity ranging from 65% to 80%. The fluff pulp wasdivided into four portions (1.425 g; 2.360 g; 2.360 g; and 2.360 g).

A 10×20 cm thermobonded polypropylene non-woven (17 g/m², Maquin S.A.,Puebla, Mexico) filter was positioned at the bottom of the molding cell(10×20 cm). The molding cell was assembled and positioned in theabsorbent member forming apparatus. Following the creation of a vacuumin the vacuum chamber, the motor was switched on. The pressurized airregulator was activated, allowing pressurized air to enter the apparatus(60 Psi, 7/64 Nozzle). The first fluff portion (1.425 g) was added usinga funnel, followed by the addition of surface-treated carboxyalkylatedpolysaccharide (1.860 g) twenty seconds later. Following a delay of 10seconds, the second fluff portion (2.360 g) was added, followed by theaddition of a further portion of surface-treated carboxyalkylatedpolysaccharide (1.860 g) twenty seconds later. Again, following a delayof 10 seconds, the third fluff portion (2.360 g) was added, followed bythe addition of a further portion of surface-treated carboxyalkylatedpolysaccharide (1.860 g) twenty seconds later. Finally, following adelay of 10 seconds, the fourth fluff portion (2.360 g) was added andthe apparatus shut-down 20 seconds later.

The molding cell was slowly removed from the absorbent member formingapparatus. The non-woven-fluff-surface-treated carboxyalkylatedpolysaccharide mixture was placed under a fitted (10×20 cm) hydraulicpress, while remaining in the molding cell. The mixture was compressedusing a force ranging from % to 1% tons (4.9 kN to 14.7 kN) over aperiod of two minutes. In an embodiment of the present disclosure,following the compression, an absorbent member having a thicknessranging from about 6.71 mm to about 7.4 mm, a density of about 0.10g/cm³, and a surface-treated carboxyalkylated starch content of about39.7% was obtained. In order to simulate a hygiene article topsheet, afurther 10×20 cm thermobonded polypropylene non-woven (17 g/m²,Industrias Maquin S.A., Puebla, Mexico) filter was placed over theabsorbent member. A laminated polyethylene film (20 g/m², Bonlam S.A.,San-Luis-Potosi, Mexico) was placed on the other side of the absorbentmember to simulate the absorbent backsheet. The absorbent members werethen stockpiled in columns ranging from 4 to 6 items and sandwichedbetween Plexiglas plates applying a pressure of 0.7 psi over a period of20 minutes.

Rewet Testing and Acquisition Rate Testing

The size of the prototype hygiene articles is small compared tocommercial “size 4” baby diapers (user size ranging from 7 to 18 kg).The amount of fluids used in the testing was adopted to the smaller sizeof the prototype articles (50 ml/30 ml/30 ml). For larger scale testing(size 4), larger volumes of fluids are used (100 ml/60 ml/60 ml).

A prototype hygiene article was positioned on a flat surface and thecenter ( 7/12^(th) of the length) was marked with a permanent marker. Around Plexiglas™ test cylinder (FIG. 4) was then placed over the markand charged with saline solution (50 ml). The chronometer was started assoon as the solution came into contact with the hygiene article. Thechronometer was stopped as soon as all of the solution had disappearedfrom the surface of the hygiene article; the elapsed time was denoted asT₁. The hygiene article was allowed to equilibrate over a period of 20minutes. The cylinder was subsequently removed and the wet surfacecovered with weighed filter papers (about 15 g, VWR West-Chester, USA,#28320-041 filter #415). An external pressure (0.7 PSI) was then appliedusing a circular stainless steel weight (3.13 Kg) having a surface areaof 63.6 cm². Alternatively, any weight providing a pressure of 0.7 PSIor 4.83 KPa may be used. The pressure was maintained for 2 minutes. Theincrease in weight of the filter papers corresponds to the amount offluid released by the hygiene article and was denoted as the firstrewet.

The cylinder was then replaced and centered over the mark. The cylinderwas charged with an additional amount of saline solution (30 ml) and thechronometer was started as soon as the solution came into contact withthe hygiene article. The chronometer was stopped as soon as all of thesolution had disappeared from the surface of the hygiene article; theelapsed time was denoted as T₂. The hygiene article was allowed toequilibrate over a period of 20 minutes. The cylinder was subsequentlyremoved and the wet surface covered with weighed filter papers (about 15g, VWR West-Chester, USA, #28320-041 filter #415). An external pressure(0.7 PSI) was then applied using a circular stainless steel weight (3.13Kg) having a surface area of 63.6 cm². The pressure was maintained for 2minutes. The increase in weight of the filter papers corresponds to theamount of fluid released by the hygiene article and was denoted as thesecond rewet.

The cylinder was then replaced and centered over the mark. The cylinderwas charged with an additional amount of saline solution (30 ml) and thechronometer was started as soon as the solution came into contact withthe hygiene article. The chronometer was stopped as soon as all of thesolution had disappeared from the surface of the hygiene article; theelapsed time was denoted as T₃. The hygiene article was allowed toequilibrate over a period of 20 minutes. The cylinder was subsequentlyremoved and the wet surface covered with weighed filter papers (about 15g, VWR West-Chester, USA, #28320-041 filter #415). An external pressure(0.7 PSI) was then applied using a circular stainless steel weight (3.13Kg) having a surface area of 63.6 cm². The pressure was maintained for 2minutes. The increase in weight of the filter papers corresponds to theamount of fluid released by the hygiene article and was denoted as thethird rewet. The total rewet corresponds to the sum of the individualrewet measurements.

The acquisition rate corresponds to the number of milliliters of salinesolution absorbed by the hygiene article, divided by the time taken toabsorb the volume of saline solution. The third acquisition rate can becalculated as follows: 30 ml/T₃=A₃ (ml/sec).

The averaged acquisition rate corresponds to the total number ofmilliliters of saline solution absorbed by the hygiene article (110 ml),divided by the total time taken to absorb the volume of saline solution.The averaged acquisition rate can be calculated as follows: 110ml/(T₁+T₂+T₃)=A_(T) (ml/sec).

EXAMPLES Citric Acid Surface-Treated Carboxymethyl Potato Starch

Water (900 ml), potato starch (297 g; 14% moisture content) and sodiumhydroxide (5.6 g; 50% solution) were added to a two-liter beaker. Themixture was stirred over a period of 35 minutes at a temperature of 40°C. Epichlorohydrin (1.197 g) was subsequently added and the mixtureallowed to react for an additional 35 minutes while stirring to producea cross-linked starch slurry. Additional sodium hydroxide (192 g; 50%solution) was added and the slurry stirred for 5 minutes producing agelatinized starch. The gelatinized starch was heated at 60° C. andmixed with sodium monochloroacetate (252 g; added stepwise over a periodof 15 minutes). The gel was left to react for a period of 1 hour,precipitated by the addition of methanol (˜7.0 liters) and filtered. Theresulting precipitate was slurried in a methanol/water solution (2.0liters; 9:1 V/V), the pH adjusted to 8.5-9.0 using hydrochloric acid andheated. The slurry was filtered, the residue re-slurried in amethanol/water solution (2.0 liters; 9:1 V/V) and filtered. An aliquot(1 ml) of the filtrate was taken and mixed with a few drops of silvernitrate. The absence of a silver chloride precipitate is indicative ofproduct purity. Where a silver chloride precipitate was observed, theproduct was re-slurried again using a methanol/water solution (2.0liters; 9:1 V/V) and filtered. This process was repeated until nofurther sliver chloride precipitation could be observed. The residue wassubsequently purified by washing with methanol (2.0 liters), filteredand dried in a convection oven at 65° C.

The dried product (300 g) was dispersed in water (2.7 liters) to form ahydrogel. The pH of the hydrogel was adjusted to 8.5-9.0. The hydrogelwas subsequently dried in a convection oven at 65° C. The dried productwas ground and sieved (20 and 100 Mesh). The sieved product (40 g) wasmixed with a citric acid solution (18.0 ml; 2.58 g of citric acid in 12ml of water and 105 ml of isopropanol). The cake was evenly spread on aPyrex™ pie dish (about 23 cm in diameter) having an even depth of about1 mm. This cake was subsequently heated in convection mode at 100° C.over a period of 19 minutes. Further heating was accomplished in an IRoven at 140° C. over a period of 15 minutes. The absorbentcharacteristics of the resulting product were subsequently measured andare summarized hereinbelow in Table 3. The ATR-IR spectrum of theproduct is shown in FIG. 5.

TABLE 3 Absorbent characteristics of citric acid surface-treated CMS FSC34.5 g/g CRC 25.0 g/g AUL (0.7 psi) 15.9 g/g Biobased 82.2% content

Hygiene articles comprising the product (citric acid surface-treatedCMS) were subsequently prepared and tested (Table 4).

TABLE 4 Hygiene article performance Third rewet 1.2 g Total rewet 1.7 gThird acquisition rate 0.25 ml/sec Averaged acquisition rate 0.14 ml/secNumber of hygiene articles tested: 16; results represent averagedvalues.

Acid Surface-Treated Carboxymethyl Potato Starch

Water (900 ml), potato starch (297 g; 14% moisture content) and sodiumhydroxide (5.6 g; 50% solution) were added to a two-liter beaker. Themixture was stirred over a period of 35 minutes at a temperature of 40°C. Epichlorohydrin (1.197 g) was subsequently added and the mixtureallowed to react for an additional 35 minutes while stirring to producea cross-linked starch slurry. Additional sodium hydroxide (192 g; 50%solution) was added and the slurry stirred for 5 minutes producing agelatinized starch. The gelatinized starch was heated at 60° C. andmixed with sodium monochloroacetate (252 g; added stepwise over a periodof 15 minutes). The gel was left to react for a period of 1 hour,precipitated by the addition of methanol (˜7.0 liters) and filtered. Theresulting precipitate was slurried in a methanol/water solution (2.0liters; 9:1 V/V), the pH adjusted to 8.5-9.0 using hydrochloric acid andheated. The slurry was filtered, the residue re-slurried in amethanol/water solution (2.0 liters; 9:1 V/V) and filtered. An aliquot(1 ml) of the filtrate was taken and mixed with a few drops of silvernitrate. The absence of a silver chloride precipitate is indicative ofproduct purity. Where a silver chloride precipitate was observed, theproduct was re-slurried again using a methanol/water solution (2.0liters; 9:1 V/V) and filtered. This process was repeated until nofurther sliver chloride precipitation could be observed. The residue wassubsequently purified by washing with methanol (2.0 liters), filteredand dried in a convection oven at 65° C.

The dried product (300 g) was dispersed in water (2.7 liters) to form ahydrogel. The pH of the hydrogel was adjusted to 8.5-9.0. The hydrogelwas subsequently dried in a convection oven at 65° C. The dried productwas ground and sieved (20 and 100 Mesh). The sieved product (15 g) wasmixed with an acidic solution (18.0 ml; 2.58 g of citric acid in 12 mlof water and 105 ml of isopropanol). For the preparation of thehydrochloric acid solution, hydrochloric acid (3,046 ml, 12N) was mixedwith isopropanol (105 ml) and water (12 ml). For the preparation of thestearic acid solution, stearic acid (10.48 g) was dissolved inisopropanol (105 ml) and water (12 ml). For the preparation of theacetic acid solution, glacial acetic acid (2.21 g) was dissolved inisopropanol (105 ml) and water (12 ml). The cake was evenly spread on aPetri dish (about 9 cm in diameter) having an even depth of about 1 mm.This cake was subsequently heated in convection mode at 100° C. over aperiod of 15 minutes. Further heating was accomplished in an IR oven at140° C. over a period of 12 minutes. The absorbent characteristics ofthe resulting product were subsequently measured and are summarizedhereinbelow in Table 5.

TABLE 5 Absorbent characteristics of acid surface-treated CMSHydrochloric acid Stearic acid Acetic acid FSC 30.0 g/g 31.5 g/g 31.3g/g CRC 18.0 g/g 22.3 g/g 21.1 g/g AUL (0.7 psi) 18.0 g/g 11.9 g/g 12.3g/g ATR-IR FIG. FIG. 6 FIG. 7

Comparison Between Dynamic and Static Heat Treatment Environments

Water (900 ml), waxy corn starch (297 g; 14% moisture content) andsodium hydroxide (2.8 g; 50% solution) were added to a two-liter beaker.The mixture was stirred over a period of 35 minutes at a temperature of40° C. Epichlorohydrin (1.197 g) was subsequently added and the mixtureallowed to react for an additional 35 minutes while stirring to producea cross-linked starch slurry. Additional sodium hydroxide (192 g; 50%solution) was added and the slurry stirred for 5 minutes producing agelatinized starch. The gelatinized starch was heated at 60° C. andmixed with sodium monochloroacetate (252 g; added stepwise over a periodof 15 minutes). The gel was left to react for a period of 1 hour,precipitated by the addition of methanol (˜7.0 liters) and filtered. Theresulting precipitate was slurried in a methanol/water solution (2.0liters; 9:1 V/V), the pH adjusted to 8.5-9.0 using hydrochloric acid andheated. The slurry was filtered, the residue re-slurried in amethanol/water solution (2.0 liters; 9:1 V/V) and filtered. An aliquot(1 ml) of the filtrate was taken and mixed with a few drops of silvernitrate. The absence of a silver chloride precipitate is indicative ofproduct purity. Where a silver chloride precipitate was observed, theproduct was re-slurried again using a methanol/water solution (2.0liters; 9:1 V/V) and filtered. This process was repeated until nofurther sliver chloride precipitation could be observed. The residue wassubsequently purified by washing with methanol (2.0 liters), filteredand dried in a convection oven at 65° C.

The dried product (100 g) was dispersed in water (900 ml) to form ahydrogel. The pH of the hydrogel was adjusted to 8.5-9.0. The hydrogelwas subsequently dried in a convection oven at 65° C. The dried productwas ground and sieved (20 and 100 Mesh).

Dynamic Environment

The sieved product (7.5 g) was mixed with a citric acid solution (18.0ml; 2.58 g of citric acid in 12 ml of water and 105 ml of isopropanol).The resulting slurry was placed in a round bottom flask equipped with amagnetic stirrer and heated over a period of 2 hours at a temperature of90° C. The resulting slurry was subsequently heated with stirring over aperiod of 30 minutes at 140° C. Finally, the product was allowed tocool. The absorbent characteristics of the resulting product weresubsequently measured and are summarized hereinbelow in Table 6.

Static Environment

The sieved product (5.0 g) was mixed with a citric acid solution (2.3ml; 2.58 g of citric acid in 12 ml of water and 105 ml of isopropanol).The resulting slurry was placed on a watch glass and transferred into aconvection oven where it was heated at 100° C. over a period of 10minutes. The watch glass was subsequently placed into a humiditybalance, equipped with an IR source and heated at 140° C. over a periodof 30 minutes. Finally, the product was allowed to cool. The absorbentcharacteristics of the resulting product were subsequently measured andare summarized hereinbelow in Table 6.

TABLE 6 Absorbent characteristics of citric acid surface-treated CMSDynamic Static FSC 32 g/g 32 g/g CRC 22 g/g 20 g/g AUL (0.7 psi) 9.0g/g  15 g/g SEM FIG. FIG. 8 FIG. 9

Impact of Heating Time on Surface-Treated Carboxymethyl Starch

The sieved product (5.0 g) from the preceding example was mixed with acitric acid solution (2.3 ml; 2.58 g of citric acid in 12 ml of waterand 105 ml of isopropanol). The resulting slurry was placed on a watchglass and transferred into a convection oven where it was heated at 100°C. over a period of 10 minutes. The product was subsequently heated at140° C. The absorbent characteristics of the resulting product(following a cooling period) were measured following a heating period at140° C. of 0.5, 1, 2 and 5 hours (FIG. 12).

Impact of Heating Time on Surface-Treated Carboxymethyl Cellulose in aConvection Oven

Carboxymethyl cellulose (Aqualon B315, 8% moisture content) was fed intothe extruder at a rate of 3.8 kg/hr. An alkaline solution (pH 8.8) wassubsequently injected at a rate of 37.6 kg/h. The extruder had thefollowing barrel temperature profile: Tb₁=27° C. Tb₂=27° C., Tb₃=27° C.,Tb₄=25° C., Tb₅=28° C., Tb₆=27° C., Tb₇=28° C., Tb₈=30° C. and Tb₉=24°C. The hydrogel product was produced at a rate of 38 kg/hr and amoisture content of 91%. The hydrogel was subsequently dried in aconvection oven at 65° C., ground and sieved. The fraction between20-100 Mesh (850 μm to 150 μm) was retained.

The sieved product (5.0 g) was mixed with a citric acid solution (2.3ml; 2.58 g of citric acid in 12 ml of water and 105 ml of isopropanol).The resulting slurry was placed on a watch glass and transferred into aconvection oven where it was heated at 100° C. for 10 minutes. Theproduct was subsequently heated at 140° C. The absorbent characteristicsof the resulting product (following a cooling period) were measuredfollowing a heating period at 140° C. of 10, 30, and 120 minutes (FIG.13).

Infra-Red Heat Treatment of CMS

Water (870 ml), wheat starch (330 g) and sodium hydroxide (5.5 g; 50%solution) were added to a two-liter beaker. The mixture was stirred overa period of 35 minutes at a temperature of 40° C. Epichlorohydrin (1.197g) was subsequently added and the mixture allowed to react for anadditional 35 minutes while stirring to produce a cross-linked starchslurry. Additional sodium hydroxide (147 g; 50% solution) was added andthe slurry stirred for 5 minutes producing a gelatinized starch. Thegelatinized starch was heated at 60° C. and mixed with sodiummonochloroacetate (213 g; added stepwise over a period of 15 minutes).The gel was left to react for a period of 1 hour, precipitated by theaddition of methanol (˜7.0 liters) and filtered. The resultingprecipitate was slurried in a methanol/water solution (2.0 liters; 9:1V/V), the pH adjusted to 8.5-9.0 using hydrochloric acid and heated. Theslurry was filtered, the residue re-slurried in a methanol/watersolution (2.0 liters; 9:1 V/V) and filtered. An aliquot (1 ml) of thefiltrate was taken and mixed with a few drops of silver nitrate. Theabsence of a silver chloride precipitate is indicative of productpurity. Where a silver chloride precipitate was observed, the productwas re-slurried again using a methanol/water solution (2.0 liters; 9:1V/V) and filtered. This process was repeated until no further sliverchloride precipitation could be observed. The residue was subsequentlypurified by washing with methanol (2.0 liters), filtered and dried in aconvection oven at 65° C.

The dried product (100 g) was dispersed in water (900 ml) to form ahydrogel. The pH of the hydrogel was adjusted to 8.5-9.0. The hydrogelwas subsequently dried in a convection oven at 65° C. The dried productwas ground and sieved (20 and 100 Mesh). The sieved product (40 g) wasmixed with a citric acid solution (18.0 ml; 5.16 g of citric acid in 24ml of water and 210 ml of isopropanol). The slurry was evenly spread ona Pyrex™ pie dish and subsequently heated in a convection oven at 100°C. over a period of 18 minutes. The process was repeated with a furtherbatch of dried product (40 g). The two samples were subsequently placedin an IR oven and heated at 140° C. and 160° C. respectively. The sampletemperatures, as measured with an IR thermometer were however differentfrom the programmed oven temperatures (Table 7). The absorbentcharacteristics of the samples (following a cooling period) weremeasured following a heating period of 5, 10, 12, 15, and 20 minutes(FIGS. 14 and 15).

TABLE 7 Programmed and Measured Temperatures Pro- grammed Temper- TimeMeasured temperature at various times ature programmed 2 min 5 min 10min 15 min 20 min 140° C.  5 minutes 121° C. 141° C. — — — 10 minutes118° C. 161° C. 160° C. — — 15 minutes 123° C. 166° C. 159° C. 162° C. —20 minutes 120° C. 141° C. 156° C. 168° C. 167° C. 160° C.  5 minutes132° C. 161° C. — — — 10 minutes 123° C. 177° C. 186° C. — — 15 minutes117° C. 160° C. 187° C. 190° C. — 20 minutes 124° C. 157° C. 184° C.194° C. 196° C. Starting temperature: 21° C.

Agglomerator Surface-Treated CMS

Water (900 ml), wheat starch (338 g; 14% moisture content) and sodiumhydroxide (5.5 g; 50% solution) were added to a two-liter beaker. Themixture was stirred over a period of 35 minutes at a temperature of 40°C. Epichlorohydrin (1.20 g) was subsequently added and the mixtureallowed to react for an additional 35 minutes while stirring to producea cross-linked starch slurry. Additional sodium hydroxide (147 g; 50%solution) was added and the slurry stirred for 5 minutes producing agelatinized starch. The gelatinized starch was heated at 60° C. andmixed with sodium monochloroacetate (214 g; added stepwise over a periodof 15 minutes). The gel was left to react for a period of 1 hour,precipitated by the addition of methanol (˜7.0 liters) and filtered. Theresulting precipitate was slurried in a methanol/water solution (2.0liters; 9:1 V/V), the pH adjusted to 8.5-9.0 using hydrochloric acid andheated. The slurry was filtered, the residue re-slurried in amethanol/water solution (2.0 liters; 9:1 V/V) and filtered. An aliquot(1 ml) of the filtrate was taken and mixed with a few drops of silvernitrate. The absence of a silver chloride precipitate is indicative ofproduct purity. Where a silver chloride precipitate was observed, theproduct was re-slurried again using a methanol/water solution (2.0liters; 9:1 V/V) and filtered. This process was repeated until nofurther sliver chloride precipitation could be observed. The residue wassubsequently purified by washing with methanol (2.0 liters), filteredand dried in a convection oven at 65° C.

The dried product (300 g) was dispersed in water (2.7 liters) to form ahydrogel. The pH of the hydrogel was adjusted to 8.5-9.0. The hydrogelwas subsequently dried in a convection oven at 65° C. The dried productwas ground and sieved (20 and 100 Mesh).

The agglomerator parameters were adjusted as follows: air flow: 20l/minute; air flow pressure: 15 psig (103 kPa); and air temperature: 70°C. About 50 g of the dried product was placed in the agglomerator. About5.0 g of a citric acid solution (9.8 g of citric acid in 100 ml ofwater) was injected through a nozzle over a period of about 2 minutes.CMS particles having a moisture content of 10% were obtained. Theparticles were placed on a Pyrex™ pie dish and placed in an IR ovenheated at a programmed temperature of 140° C. over a period of 12minutes (the measured temperature after 12 minutes was about 160° C.).The product was allowed to cool and the absorbent characteristicsmeasured (Table 8).

TABLE 8 Agglomerator treated CMS characteristics FSC 29 g/g CRC 16 g/gAUL (0.7 psi) 17 g/g Physical Discrete gel appearance of particlesswollen gel

Citric Acid Surface-Treated Carboxymethyl Wheat Starch

Water (900 ml), wheat starch (337 g; 12% moisture content) and sodiumhydroxide (5.5 g; 50% solution) were added to a two-liter beaker. Themixture was stirred over a period of 35 minutes at a temperature of 40°C. Epichlorohydrin (1.204 g) was subsequently added and the mixtureallowed to react for an additional 35 minutes while stirring to producea cross-linked starch slurry. Additional sodium hydroxide (192 g; 50%solution) was added and the slurry stirred for 5 minutes producing agelatinized starch. The gelatinized starch was heated at 60° C. andmixed with sodium monochloroacetate (213 g; added stepwise over a periodof 15 minutes). The gel was left to react for a period of 1 hour,precipitated by the addition of methanol (˜7.0 liters) and filtered. Theresulting precipitate was slurried in a methanol/water solution (2.0liters; 9:1 V/V), the pH adjusted to 8.5-9.0 using hydrochloric acid andheated. The slurry was filtered, the residue re-slurried in amethanol/water solution (2.0 liters; 9:1 V/V) and filtered. An aliquot(1 ml) of the filtrate was taken and mixed with a few drops of silvernitrate. The absence of a silver chloride precipitate is indicative ofproduct purity. Where a silver chloride precipitate was observed, theproduct was re-slurried again using a methanol/water solution (2.0liters; 9:1 V/V) and filtered. This process was repeated until nofurther sliver chloride precipitation could be observed. The residue wassubsequently purified by washing with methanol (2.0 liters), filteredand dried in a convection oven at 65° C.

The dried product (300 g) was dispersed in water (2.7 liters) to form ahydrogel. The pH of the hydrogel was adjusted to 8.5-9.0. The hydrogelwas subsequently dried in a convection oven at 65° C. The dried productwas ground and sieved (20 and 100 Mesh). The sieved product (40 g) wasmixed with a citric acid solution (18.0 ml; 2.58 g of citric acid in 12ml of water and 105 ml of isopropanol). The slurry was evenly spread ona Pyrex™ pie dish (about 23 cm in diameter) having an even depth ofabout 1 mm. This cake was subsequently heated in convection mode at 100°C. over a period of 19 minutes. Further heating was accomplished in anIR oven at 140° C. over a period of 15 minutes. The absorbentcharacteristics of the resulting product were subsequently measured andare summarized hereinbelow in Table 9.

TABLE 9 Absorbent characteristics of citric acid surface-treated CMS(wheat) FSC 29.7 g/g CRC 18.7 g/g AUL (0.7 psi) 16.2 g/g

Manufacture of Carboxyalkylated Starches by Reactive Extrusion

Wheat starch having a moisture content of 11% was fed into a TSE (ZSE 40mm) using an agitated gravimetric feeder, at a throughput of 9.25 kg/hr(20.4 lbs/hr). Sodium monochloroacetate was concomitantly fed into theextruder (gravimetric feeder) at a throughput of 4.2 kg/hr (9.3 lbs/hr).A sodium hydroxide solution (36%) was injected at a throughput of 4.03kg/hr (8.9 lbs/hr). The water content of the wheat starch was increasedto about 20.6%. The extruder had the following barrel temperatureprofile: Tb₂=29° C. Tb₃=29° C., Tb₄=32° C., Tb₅=43° C., Tb₆=65° C.,Tb₇=121° C., Tb₈=101° C., Tb₉=87° C. and Tb₁₀=85° C. The screw speed wasset at 200 rpm and the screw load at 34%. The TSE was equipped with adie comprising 10 holes (3 mm in diameter). The die discharge pressurewas 144 kPa (21 Psig). The extrudate had a temperature of 102° C. Theextrudate was subsequently oven dried to a moisture content of 6.7%,ground and sieved (16 and 50 Mesh being the fraction retained). The DSwas characterized according to method ASTM D1439-83a. A reactionefficiency of 80% was obtained.

The dried product (85 g) was dispersed in a methanol/water solution (500ml; 85:15 V/V) at 60° C. for 90 minutes. The conductance was measured tobe 8300 μS/cm; the pH was recorded to be 8.5. The product was filteredand dispersed in a methanol/water solution (500 ml; 85:15 V/V) at 60° C.for 90 minutes. The conductance was measured to be 3030 μS/cm; the pHwas recorded to be 8.4. The product was filtered and dispersed in amethanol/water solution (500 ml; 85:15 V/V) at 60° C. for 90 minutes.The conductance was measured to be 2250 μS/cm; the pH was recorded to be8.5. The product was filtered and dispersed in a methanol/water solution(500 ml; 85:15 V/V) at 60° C. for 90 minutes. The conductance wasmeasured to be 900 μS/cm; the pH was recorded to be 8.3. The product wasfiltered and dispersed in a methanol/water solution (500 ml; 85:15 V/V)at 60° C. for 90 minutes. The conductance was measured to be 670 μS/cm;the pH was recorded to be 8.5. The product was filtered and dispersed ina methanol/water solution (500 ml; 85:15 V/V) at 60° C. for 90 minutes.The conductance was measured to be 450 μS/cm; the pH was recorded to be8.5. The product was filtered and dispersed in a methanol/water solution(500 ml; 85:15 V/V) at 60° C. for 90 minutes. The conductance wasmeasured to be 485 μS/cm; the pH was recorded to be 8.5. The product wasfinally filtered and dried in a convection oven at 65° C.

The dried product (5.0 g) was mixed with a citric acid solution (2.3 ml;2.58 g of citric acid in 12 ml of water and 105 ml of isopropanol). Theslurry was evenly spread on a watch glass and heated in convection modeat 100° C. over a period of 10 minutes. Further heating was accomplishedin an IR oven at 140° C. over a period of 12 minutes. The absorbentcharacteristics of the resulting product were subsequently measured andare summarized hereinbelow in Table 10.

TABLE 10 Absorbent characteristics of citric acid surface-treated CMS(wheat) FSC 33 g/g CRC 20 g/g AUL (0.7 psi) 16 g/g

In an embodiment of the present disclosure, starch was fed into theextruder at a throughput of 28.0 lbs/hr. Sodium monochloroacetate wasconcomitantly fed into the extruder at a throughput of 13.0 lbs/hr. Tapwater was injected through a first nozzle positioned 400 mm downstreamthe extruder, at a rate of 4.8 lbs/hr. A sodium hydroxide solution (50%)was injected through the nozzle at a rate of 9.0 lbs/hr. The subsequentpurification and surface-treatment was carried out according to theprotocol as described hereinabove. The product was subsequently analyzedby SEM (FIGS. 8 and 9)

It is to be understood that the disclosure is not limited in itsapplication to the details of construction and parts as describedhereinabove. The disclosure is capable of other embodiments and of beingpracticed in various ways. It is also understood that the phraseology orterminology used herein is for the purpose of description and notlimitation. Hence, although the present disclosure has been describedhereinabove by way of illustrative embodiments thereof, it can bemodified without departing from the spirit, scope and nature as definedin the appended claims.

1-70. (canceled)
 71. A superabsorbent material comprising: a particleformed of a carboxyalkylated starch having a pH in a range from about5.0 to about 10, said particle having an interior and a surface, each ofwhich exhibiting a differentiated functionality; said interior isabsorbent; said surface is treated with a non-crosslinking acid, suchthat penetration depth of said non-crosslinking acid is limited to saidsurface; and said carboxyalkylated starch has a homogeneouscarboxyalkylated substitution pattern.
 72. The superabsorbent materialaccording to claim 71, wherein said carboxyalkylated starch exhibits anester linkage as characterized by the presence of an ester shoulder orester band as determined by ATR-IR spectroscopy.
 73. The superabsorbentmaterial according to claim 71, wherein said non-crosslinking acid isselected from the group consisting of organic monovalent acids andinorganic monovalent acids.
 74. The superabsorbent material according toclaim 73, wherein said non-crosslinking acid is at least: hydrochloricacid, stearic acid, and citric acid.
 75. The superabsorbent materialaccording to claim 1, wherein said carboxyalkylated starch exhibits asubstitution degree ranging from 0.2 to 1.0.
 76. The superabsorbentmaterial according to claim 5, wherein said carboxyalkylated starchexhibits a substitution degree ranging from 0.4 to 0.7.
 77. Thesuperabsorbent material according to claim 1, wherein saidcarboxalkylated starch is carboxyalkylated in an aqueous alkalinemedium.
 78. A superabsorbent material comprising: a particle formed of acarboxyalkylated polysaccharide having a pH in a range from about 5.0 toabout 10, said particle having an interior and a surface, eachexhibiting a differentiated functionality; said interior is absorbent;said surface is treated with a non-crosslinking acid, such thatpenetration depth of said non-crosslinking acid is limited to saidsurface, said non-crosslinking acid induces ester linkages betweenpolysaccharide strands at said particle surface, which imparts saidparticle with a sufficient structural rigidity to enable said particleto maintain a discrete particle shape when contacted with a saltsolution, and said carboxyalkylated polysaccharide particle has agreater absorbance under load (AUL) of said salt solution at 0.7 psithan a comparative particle formed of the carboxyalkylatedpolysaccharide having a surface that is not treated with thenon-crosslinking acid.
 79. A hygiene article comprising an absorbentmember, said absorbent member includes from 15% to 80% of a carboxylatedpolysaccharide particle, said carboxylated polysaccharide particlehaving an external surface treated with a non-crosslinking acid, suchthat penetration depth of said non-crosslinking acid is limited to saidsurface, and said carboxylated polysaccharide particle having ahomogeneous carboxyalkylated substitution pattern.
 80. The hygienearticle according to claim 79, wherein said hygiene article ischaracterized by properties selected from the group consisting of: athird acquisition rate of at least 0.22 ml/sec; a third rewet of at most4.0 grams; an averaged acquisition rate of at least 0.12 ml/sec., and atotal rewet of at most 6.0 grams.
 81. The hygiene article according toclaim 79, wherein said hygiene article is at least one of the following:diapers, incontinence articles, feminine hygiene products, sanitarynapkins, absorbent dressings, absorbent paper products, textileproducts, printing products, air-laids, household articles, food pads,animal litter products, and sealing materials.
 82. A process of making acarboxyalkylated polysaccharide particle, comprising: treating aglass-like polysaccharide particle with a non-crosslinking acid, suchthat penetration depth of said non-crosslinking acid is limited to asurface of said glass-like polysaccharide particle, such that saidnon-crosslinking acid generates ester linkages between polysaccharidestrands at said particle surface, which imparts said particle with asufficient structural rigidity to enable said particle to maintain adiscrete particle shape when contacted with a salt solution.
 83. Theprocess of claim 82, wherein said glass-like polysaccharide particle isinternally cross-linked prior to carboxyalkylating.
 84. The process ofclaim 82, wherein said glass-like polysaccharide particle iscarboxyalkylated in an alkaline medium.
 85. The process of claim 84,wherein said alkaline medium is either: a dry alkali medium, an aqueousalkaline hydrophilic organic solvent, or aqueous alkaline solution. 86.The process of claim 82, wherein said carboxyalkylated polysaccharide iscarboxyalkylated in a reactive extrusion.
 87. The process of claim 86,wherein said carboxyalkylated polysaccharide is carboxyalkylated in anextrusion with a water content ranging from 15% to 30%.
 88. The processof claim 86, wherein carboxyalkylated polysaccharide is carboxyalkylatedin a reactive extrusion exhibiting at least of 60% efficiency.
 89. Theprocess of claim 86, wherein said reactive extrusion involves using atwin screw extruder.